• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.72-75
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• 2004

The potential of electrokinetic (EK) technology has been successfully demonstrated for the remediation of heavy metal contaminated fine-grained soils through laboratory scale and field application studies. Arsenic contamination in soil is a serious problem affecting both site use and groundwater quality. The EK technology was evaluated for the removal of arsenic from two soil samples: kaolinite clay artificially contaminated with arsenic and arsenic-bearing tailing soil taken from the Myungbong (MB) mining area. The effect of cathodic electrolyte on the process was investigated using three different types of electrolyte: deionized water (DIW), potassium phosphate (KH$_2$PO$_4$) and sodium hydroxide (NaOH). The result of experiments on the kaolinite clay shows that the potassium phosphate was most effective in extracting arsenic, probably resulting from anion exchange of arsenic species by phosphate. On the contrary, the sodium hydroxide seemed to be most efficient in removing arsenic from the tailing soil, and it is explained by the fact that sodium hydroxide increased the soil pH and accelerated ionic migration of arsenic species through increase in desorption and dissolution of arsenic species into pore water.

• Journal of Korean Society of Rural Planning
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• v.24 no.3
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• pp.63-71
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• 2018

The comparison of demand and supply is needed for efficient ecosystem services planning. However, the gap between them cannot be analyzed as existing studies mainly dealt with only the supply of ecosystem services. This study compares the demand and supply of ecosystem services in Shiheung using environmental complaints and urban planning by semantic network analysis. As a result, 'air' and 'water' quality are magnified in demand, 'energy' and 'water' are crucial in supply. This result presents that citizen ask for the improvement of air quality in regulation services, although local government has plans for energy support in provisioning services. Periodic ecosystem services demand and supply monitoring will be the base of effective ecosystem services planning, which reduce insufficiency and surplus.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.3-32
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• 2008

The potential deep geothermal resources span a wide range of heat sources from the earth, including not only the more easily developed, currently economic hydrothermal resources; but also the earth's deeper, stored thermal energy, which is present anywhere. At shallow depths of 3,000~10,000m, the coincidence of substantial amounts heat in hot rock, fluids that heat up while flowing through the rock and permeability of connected fractures can result in natural hot water reservoirs. Although conventional hydrothermal resources which contain sufficient fluids at high temperatures and geo-pressures are used effectively for both electric and nonelectric applications in the world, they are somewhat limited in their location and ultimate potential for supplying electricity. A large portion of the world's geothermal resource base consists of hot dry rock(HDR) with limited permeability and porosity, an inadquate recharge of fluids and/or insufficient water for heat transport. An alternative known as engineered or enhanced geothermal systems(EGS), to dependence on naturally occurring hydrothermal reservoirs involves human intervention to engineer hydrothermal reservoirs in hot rocks for commercial use. Therefore EGS resources are with enormous potential for primary energy recovery using an engineered heat mining technology, which is designed to extract and utilize the earth's stored inexthermal energy. Because EGS resources have a large potential for the long term, United States focused his effort to provide 100GW of 24-hour-a-day base load electric-generating capacity by 2050.

• Korean Journal of Environment and Ecology
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• v.29 no.2
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• pp.228-235
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• 2015

Stream ecosystems are closely related to many human activities. Therefore, streams are affected by anthropogenic disturbances such as riverine development and gravel-mining as well as deterioration of water quality. The goal of this study was to elucidate the recolonization process of the macroinvertebrate community after a small-scale anthropogenic disturbance. Field studies were conducted at three sites in a natural stream. The number of recolonizing species tended to increase slightly over time, exceeding the total species number of the control. Ephemeroptera contributed the most to shaping the recolonizing pattern of the entire community. From the result of changes in dominant species, the early recolonizers of each site were the species that showed more frequent occurrence particulary at each sites. But the late recolonizers are Chironomidae at all the sites commonly. This result implies that the actual differences exist among the recolonizing trends of each benthic macroinvertebrate taxon. Collector-gatherers and scrapers comprised about 70% of the recolonizing species. These results indicate that the recolonizing process of an aquatic community after an artificial disturbance depends on the environmental conditions(particularly substratum composition or organic pollution) of the habitat.

• Geomechanics and Engineering
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• v.13 no.6
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• pp.947-961
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• 2017

An innovative spiral variable-section capillary model is established for piping critical hydraulic gradient of cohesion-less soils causing water/mud inrush in tunnels. The relationship between the actual winding seepage channel and grain-size distribution, porosity, and permeability is established in the model. Soils are classified into coarse particles and fine particles according to the grain-size distribution. The piping critical hydraulic gradient is obtained by analyzing starting modes of fine particles and solving corresponding moment equilibrium equations. Gravities, drag forces, uplift forces and frictions are analyzed in moment equilibrium equations. The influence of drag force and uplift force on incipient motion is generally expounded based on the mechanical analysis. Two cases are studied with the innovative capillary model. The critical hydraulic gradient of each kind of sandy gravels with a bimodal grain-size-distribution is obtained in case one, and results have a good agreement with previous experimental observations. The relationships between the content of fine particles and the critical hydraulic gradient of seepage failure are analyzed in case two, and the changing tendency of the critical hydraulic gradient is accordant with results of experiments.

• Advances in concrete construction
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• v.3 no.1
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• pp.55-69
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• 2015

Tailing Material (TM) and Fly Ash (FA) are obtained as waste products from the mining and thermal industries. Studies were carried out to explore the possibility of utilizing TM as a part replacement to fine aggregate and FA as a part replacement to cement, in concrete mixes. The effect of replacing fine aggregate by TM and cement by FA on the standard sized specimen for compressive strength, split tensile strength, and flexural strengths are evaluated in this study. The concrete mix of M40 grade was adopted with water cement ratio equal to 0.40. Concrete mix with 35% TM and 65% natural sand (TM35/S65) has shown superior performance in strength as against (TM0/S100, TM30/S70, TM40/S60, TM50/S50, and TM60/S40). For this composition, studies were performed to propose the optimal replacement of Ordinary Portland Cement (OPC) by FA (Replacement levels studied were 20%, 30%, 40% and 50%). Replacement level of 20% OPC by FA, has shown about 0-5% more compressive strength as against the control mix, for both 28 day and 56 days of water curing. Interestingly results of split tensile and flexural strengths for 20% OPC replaced by FA, have shown strengths equal to that of no replacement (control mix).

• Geomechanics and Engineering
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• v.17 no.2
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• pp.133-143
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• 2019

An optimal hydraulic section is critical for irrigated water conservancy in seasonal frozen ground due to a large proportion of water leakage, as investigated by in-situ surveys. This is highly correlated with the frost heave of underlain soils in cold season. This paper firstly derived a practical model for frost heave of clayey soils, with temperature dependent thermal indexes incorporating phase change effect. A model test carried out on clay was used to verify the rationality of the model. A novel approach for optimizing the cross-section of irrigation canals in cold regions was suggested with live updated geometry characterized by three unique geometric constraints including slope of canal, ratio of practical flow section to the optimal and lining thickness. Allowable frost heave deformation and tensile stress in canal lining are utilized as standard in computation iterating with geometry updating while the construction cost per unit length is regarded as the eventual target in optimization. A typical section along the Jinghui irrigation canal was selected to be optimized with the above requirements satisfied. Results prove that the optimized hydraulic section exhibits smaller frost heave deformation, lower tensile stress and lower construction cost.

• Journal of Korean Society of Rural Planning
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• v.27 no.4
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• pp.83-96
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• 2021

This study analyzes the perception of public value created by Korea Rural Community Corporation, a representative public corporation in the agricultural and rural sector. We categorize agricultural and rural public values as 'stable food supply,' 'conservation of national environment and nature,' 'formation and cultivation of water resources,' 'prevention of soil loss and flooding,' 'conservation of ecological system,' 'conservation of rural tradition and culture.' For the qualitative analysis, we apply content analysis. And, for the quantitative analysis, we use topic modeling and Latent Dirichlet Allocation (LDA) analysis which is used widely in the field of text-mining. Results show that internal perception for value suppliers are mainly created for 'stable food supply,' 'formation and cultivation of water resources,' and 'conservation of rural tradition and culture.' External perception for value demanders are created for all public values, but its evaluation and demand include various aspects including both positive and negative opinions.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.193-193
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• 2021

전 세계적으로 기후변화가 지속되면서 그에 따른 자연재난의 강도와 발생 빈도가 증가하고 있다. 자연재난의 발생 유형 중 집중호우와 태풍으로 인한 수문학적 재난이 대부분을 차지하고 있으며, 홍수피해는 지역적 수문학적 특성에 따라 피해의 규모와 범위가 달라지는 경향을 보인다. 이러한 이질적인 피해를 관리하기 위해서는 많은 홍수피해 정보를 수집하는 것이 필연적이다. 정보화 시대인 요즘 방대한 양의 데이터가 발생하면서 '빅데이터', '머신러닝', '인공지능'과 같은 말들이 다양한 분야에서 주목을 받고 있다. 홍수피해 정보에 대해서도 과거 국가에서 발간하는 정보외에 인터넷에는 뉴스기사나 SNS 등 미디어를 통하여 수많은 정보들이 생성되고 있다. 이러한 방대한 규모의 데이터는 미래 경쟁력의 우위를 좌우하는 중요한 자원이 될 것이며, 홍수대비책으로 활용될 소중한 정보가 될 수 있다. 본 연구는 인터넷기반으로 한 홍수피해 현상 조사를 통해 홍수피해 규모에 따라 발생하는 홍수피해 현상을 파악하고자 하였다. 이를 위해 과거에 발생한 홍수피해 사례를 조사하여 강우량, 홍수피해 현상 등 홍수피해 관련 정보를 조사하였다. 홍수피해 현상은 뉴스기사나 보고서 등 미디어 정보를 활용하여 수집하였으며, 수집된 비정형 형태의 텍스트 데이터를 '텍스트 마이닝(Text Mining)' 기법을 이용하여 데이터를 정형화 및 주요 홍수피해 현상 키워드를 추출하여 데이터를 수치화하여 표현하였다.

• Geomechanics and Engineering
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• v.37 no.4
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• pp.359-370
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• 2024

The primary goal of this study is to evaluate the migration of fine granular materials into overlying layers under cyclic loading using a modified large-scale triaxial system as a physical model test. Samples prepared for the modified large-scale triaxial system comprised a 60 mm thick gravel layer overlying a 120 mm thick subgrade layer, which could be either tailings or railway sand. A quantitative analysis of the migration of fine granular materials was based on the mass percentage and grain size of migrated materials collected in the gravel. In addition, the cyclic characteristics, i.e., accumulated axial strain and excess pore water pressure, were evaluated. As a result, the total migration rate of the railway sand sample was found to be small. However, the total migration rate of the sample containing tailings in the subgrade layer was much higher than that of the railway sand sample. In addition, the migration analysis revealed that finer tailings particles tended to be migrated into the upper gravel layer easier than coarser tailings particles under cyclic loading. This could be involved in significant increases in excess pore water pressure at the last cycles of the physical model test.